Countercurrent reaction vessel

ABSTRACT

A reaction vessel for processing liquid petroleum or chemical streams wherein the stream flows countercurrent to the flow of a treat gas, such as a hydrogen-containing gas, in at least one interaction zone. The reaction vessel contains vapor, and optionally liquid, passageways to bypass one or more packed beds, preferably catalyst beds. This permits more stable and efficient vessel operation.

FIELD OF THE INVENTION

The present invention relates to a reaction vessel for processing liquidpetroleum or chemical streams wherein the stream flows countercurrent tothe flow of a treat gas, such as a hydrogen-containing gas, in at leastone interaction zone. The reaction vessel contains vapor, and optionallyliquid, passageways to bypass one or more packed beds, preferablycatalyst beds. This permits more stable and efficient vessel operation.

BACKGROUND OF THE INVENTION

There is a continuing need in the petroleum refining and chemicalindustries for improved catalysts and process technology. One suchprocess technology, hydroprocessing, has been subjected to increasingdemands for improved heteroatom removal, aromatic saturation, andboiling point reduction. More active catalysts and improved reactionvessel designs are needed to meet this demand. Countercurrent reactionvessels have the potential of helping to meet these demands because theyoffer certain advantages over co-current flow reactors. Countercurrenthydroprocessing is well known, but of very limited commercial use. Acountercurrent process is disclosed in U.S. Pat. No. 3,147,210 whichteaches a two-stage process for the hydroprocessing-hydrogenation ofhigh boiling aromatic hydrocarbons. The feedstock is first subjected tocatalytic hydroprocessing, preferably in co-current flow with hydrogen.It is then subjected to hydrogenation over a sulfur-sensitive noblemetal hydrogenation catalyst countercurrent to the flow of ahydrogen-rich gas. U.S. Pat. Nos. 3,767,562 and 3,775,291 disclose asimilar process for producing jet fuels, except the jet fuel is firsthydrodesulfurized prior to two-stage hydrogenation. U.S. Pat. No.5,183,556 also discloses a two-stage concurrent-countercurrent processfor hydrofining--hydrogenating aromatics in a diesel fuel stream.

An apparatus is disclosed in U.S. Pat. No. 5,449,501 that is designedfor catalytic distillation. The distillation apparatus, which is avessel, contains vapor passageways which provide a means for vaporcommunication between fractionation sections located above and belowcatalyst beds. Substantially all of the vapor in the vessel risesthrough the vapor passageways and the desired contacting between vaporand liquid occurs in the fractionation sections.

While the concept of countercurrent hydroprocessing has been known forsome time, countercurrent flow reaction vessels are typically not usedin the petroleum industry, primarily because conventional countercurrentreaction vessels are susceptible to catalyst bed flooding. That is, therelatively high velocity of the upflowing treat gas prevents thedownward flow of the liquid. The liquid thus cannot pass through thecatalyst bed. While flooding is undesirable, catalyst contacting by thereactant liquid improves as the bed approaches a flooded condition.However, operating close to the point of incipient flooding leaves theprocess vulnerable to fluctuations in pressure or temperature or inliquid or gas flow rates. This could result in a disturbance largeenough to initiate flooding, and process unit shutdown in order torecover stable operation. Such disruptions are highly undesirable in acontinuous commercial operation.

Therefore, there still exists a need for improved countercurrentreaction vessel designs which are not as readily susceptible toflooding, or which can more easily recover without shutdown shouldflooding occur.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a reactionvessel for reacting liquid petroleum and chemical streams with ahydrogen-containing treat gas in the presence of a catalyst in at leastone countercurrent reaction zone, which reaction vessel comprises:

(a) a cylindrical outer shell having an enclosed top section and anenclosed bottom section;

(b) at least one liquid inlet means and at least one vapor outlet meansat a location upstream from the uppermost countercurrent reaction zonein relation to the flow of said liquid feed stream;

(c) at least one liquid outlet means and at least one gas inlet means ata location downstream of the lowermost countercurrent reaction zone;

(d) at least one reaction zone for containing a bed of catalyst, whereineach reaction zone has a non-reaction zone immediately above andimmediately below it; and

(e) at least one vapor passageway means which bypasses at least aportion of at least one countercurrent reaction zone so that a portionof the vapor within the reaction vessel can flow upward from onenon-reaction zone below said countercurrent reaction zone to anon-reaction zone above said countercurrent reaction zone without cominginto contact with at least a portion of the catalyst of saidcountercurrent reaction zone.

In one embodiment of the present invention the reaction vessel containstwo or more reaction zones.

In another embodiment of the present invention at least one of the vaporpassageways is external to the reaction vessel.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 hereof is a reaction vessel of the present invention showingthree reaction zones, each of which contains vapor passageways so thatupflowing vapor can bypass a reaction zone, and one liquid drain means.

FIG. 2 is a representation of how the reaction vessel of FIG. 1 willrespond to a flooding situation while actions are taken to return bedhydrodynamics to normalcy.

DETAILED DESCRIPTION OF THE INVENTION

The reaction vessels of the present invention are suitable for use inany petroleum or chemical process wherein it is advantageous to pass agas, such as a hydrogen-containing treat gas, countercurrent to the flowof liquid feedstock. Non-limiting examples of refinery processes inwhich the instant reaction vessels can be employed include thehydroconversion of heavy petroleum feedstocks to lower boiling products;the hydrocracking of distillate boiling range feedstocks; thehydrotreating of various petroleum feedstocks to remove heteroatoms,such as sulfur, nitrogen, and oxygen; the hydrogenation of aromatics;and the hydroisomerization and/or catalytic dewaxing of waxes,particularly Fischer-Tropsch waxes; and demetallation of heavy streams.It is preferred that the reaction vessels of the present invention bethose in which a hydrocarbon feedstock is hydrotreated and hydrogenated,more specifically when heteroatoms are removed and when at least aportion of the aromatic fraction of the feed is hydrogenated.

In countercurrent processing, the vertically upflowing gas hinders thedownward movement of the liquid. At low liquid and gas velocities, thehindrance from the slowly moving gas is not enough to cause flooding andthe liquid in the reaction vessel is able to drain through the catalystbed or beds. However, if either the upflowing gas rate or thedownflowing liquid rate is too high, liquid cannot drain through thecatalyst bed. This is known as "flooding." The liquid holdup in the bedincreases and liquid may begin to accumulate above the top surface ofthe bed. The upflowing gas rate at which flooding occurs in a given bedwill depend on such things as the rate and physical properties of thedownflowing liquid. Similarly, the downflowing liquid rate at whichflooding occurs in a given bed similarly depends on the rate andproperties of upflowing gas.

The reaction vessels of the present invention are less susceptible toflooding than conventional countercurrent reaction vessels because ofvapor passageways which act to selectively bypass a fraction of theupward-flowing treat gas through one or more of the catalyst beds. Thefraction of upflowing treat gas that bypasses a catalyst bed increasesas vapor pressure drop increases through the catalyst bed. Thus, thevapor passageways provide a self-adjusting regulation of upward-flowingvapor, thereby extending the hydrodynamic operating window of thereaction vessel. Further extension of this range can be provided byincluding one or more external vapor passageways with flow controlmeans. Such a system provides a means by which catalyst bed pressuredrop, and therefore catalyst contacting efficiency, can be controlled.Preferably, when both internal and external vapor passageways areprovided, the external vapor passageways can be controlled with acontrol means, preferably a valve for so-called "trim" bypassing. Thevalve of course can be automatically controlled so that it opens andcloses to the appropriate degree in response to a signal transmitted inresponse to pressure drop changes in the catalyst bed(s). That is, thetrim bypass will be used to keep the reaction vessel operating as closeto flooding as desirable. The treat gas which does not bypass aparticular catalyst bed or beds will pass through the other catalystbed(s) and serve to take part in the desired hydroprocessing reactions,carry away light or vaporized reaction products, strip catalyst poisonssuch as hydrogen sulfide, water and/or ammonia, etc.

Thus, the vapor passageways provide an extended operating range and anopportunity to operate close to the flooding point of the reactionvessel. This enables a more stable, more efficient reaction vesseloperating regime. Further, the reaction vessel can safely andcontinuously operate while responding to normal process fluctuations inliquid and vapor flow rate and temperature. The range of total flowrates that can be tolerated is thereby extended. Operating close to theflooding point results in very efficient contacting because the catalystparticles are well irrigated by the downflowing liquid. In the absenceof vapor passageways, a conventional countercurrent reaction vesselwould need to operate at lower efficiency in order to remain operable.

The higher vapor flow rate capacity of the reaction vessels of theinstant invention provides flexibility to use higher quench gas ratesand/or treat gas rates, enabling wider breadth of application forreactions involving high hydrogen consumption and heat release, such asaromatics saturation. Furthermore, the higher gas handling capacityenables the use of countercurrent reaction processing for reactionsinvolving evolution of vapor phase products which might otherwise resultin flooding due to excessive vapor generated during reaction, e.g.,hydrocracking.

When flooding does occur, the reaction vessels of the present inventionare also more easily recovered and brought back to normal operation.During flooding, the liquid holdup in the bed increases and liquid maybegin to accumulate above the top surface of the bed. This liquid backupmust be drained to recover from flooding. The vapor passageways reducethe gas flow rate through the catalyst bed(s), allowing the liquid tomore easily drain through the catalyst bed(s). The liquid drain means ofthe present invention also helps recover the reaction vessel fromflooding.

Unless otherwise stated herein, the terms "downstream" and "upstream"are with respect to the flow of liquid which will flow downward.Further, the vessels of the present invention need not be limited tocatalytic chemical reactions, but can also be used in gas-liquidcontacting towers such as those used for extraction or stripping. Insuch cases, no reaction is necessarily involved and the upward-movinggas contacts a downward-moving liquid, typically to achieve masstransfer between the two streams.

The reaction vessels of the present invention can be better understoodby a description of an example reaction vessel, which is shown in FIGS.1 and 2 hereof. Miscellaneous reaction vessel internals, such as flowdistributor means, thermocouples, heat transfer devices etc. are notshown in the figures for simplicity. FIG. 1 shows reaction vessel Rwhich contains liquid inlet LI for receiving a feedstock to be treated,and a liquid outlet port LO for removing liquid reaction product. Thereis also provided treat gas inlet port GI and gas outlet GO. The reactionvessel contains three serially disposed reaction zones, r₁, r₂, and r₃.Each reaction zone is immediately preceded and immediately followed by anon-reaction zone, nr₁, nr₂, nr₃, and nr₄. The non-reaction zone may bea void, or empty, section in the vessel. Liquid distribution means LR(which is not shown in FIG. 2 for simplicity ) can be situated aboveeach reaction zone in order to more evenly distribute downflowing liquidto the next downstream reaction zone. Each reaction zone is comprised ofa bed of catalyst suitable for the desired reaction.

Five vapor passageways VB₁, VB₂, VB₃, VB₄, and VB₅ and one liquid drainmeans LD are shown for the reaction vessels of the Figures, although anynumber and size of the vapor passageways can be used depending on theportion of the vapor one wishes to bypass the reaction zone(s). Forpurposes of the present invention, it is desirable that only a portionof the vapor bypass one or more countercurrent reaction zones. It ispreferred that less than about 50 vol. % be bypassed when possible. Theliquid drain means serves as a vapor passageway during normal operationbut can allow liquid to drain during flooding upsets. It is to beunderstood that more than one liquid drain means can be used in any oneor more reaction zones. The size and number of such liquid drain meanswill be dependent on such things as the size of the reaction vessel, thepacking of the catalyst in the catalyst bed(s) and the flow rate ofliquid through the catalyst bed.

The reaction vessel of FIG. 1 is operated by introducing the feedstock10 to be treated into liquid inlet LI of reaction vessel R. A suitabletreat gas, such as a hydrogen-containing gas, is introduced via port GIinto the reaction vessel countercurrent to the downward flow of theliquid feedstock. It is to be understood that the treat gas need not beintroduced solely at the bottom of the reaction vessel at port GI, butmay also be introduced into any one or more of the non-reaction zones,for example at port GI_(a) and/or GI_(b). Treat gas can also be injectedinto any one or more of the catalyst beds. An advantage of introducingtreat gas at various points in the reaction vessel is to control thetemperature within the reaction vessel. For example, cold treat gas canbe injected into the reaction vessel at various points to moderate anyexothermic heat of reaction. It is also within the scope of thisinvention that all of the treat gas can be introduced at any one of theaforesaid points as long as at least a portion of it flowscountercurrent to the flow of liquid in at least one reaction zone.

The reaction vessels used in the practice of the present invention areoperated at suitable temperatures and pressures for the desiredreaction. For example, typical hydroprocessing temperatures will rangefrom about 40° C. to about 450° C. at pressures from about 50 psig toabout 3,000 psig., preferably 50 to 2,500 psig. The liquid feedstockpasses downward through the catalyst bed of reaction zone r₁, where itreacts with the treat gas on the catalyst surface. Any resultingvapor-phase reaction products are swept upwards by the upward-flowingtreat gas. Such vapor-phase reaction products may include relatively lowboiling hydrocarbons and heteroatom components, such as H₂ S and NH₃.Any unreacted feedstock, as well as liquid reaction product passdownwardly through each successive catalyst bed of each successivereaction zone r₂ and r₃. This Figure shows an optional liquiddistribution means LR which can be positioned above each catalyst bed.The ends of the vapor passageways may be situated above or below theliquid distribution means. For example, FIG. 1 shows the upper end ofvapor passageway VB₃ terminating at a point above liquid distributionmeans LR. The lower end of vapor passageways VB₁ and VB₂ terminate at apoint below the liquid redistribution means LR. This arrangement allowsselective bypassing of vapors produced in reaction zone r₂ to thereaction vessel gas outlet, while bringing a higher purityhydrogen-containing treat gas into catalyst bed of the reaction zone r₁by selectively bypassing higher-purity hydrogen-containing gas from nr₃to the inlet of catalyst bed r₁. It is within the scope of thisinvention that the upper or lower ends of one or more of the vaporpassageways terminate at a point within the reaction zone, such as, forexample, when catalyst particles of two different sizes or geometriesare employed in a single reaction zone in layers. The exact type ofliquid distribution means is not believed to limit the practice of thepresent invention and the reaction vessel may therefore employ anyconventional distribution trays, such as sieve trays, bubble cap trays,etc. The liquid effluent exits the reaction vessel via port LO and vaporeffluent via port GO. The preferred mode of operation of the reactionvessels used in the practice of the present invention is to bypass onlya portion of the vapor while still maintaining enough vapor upflowingthrough the catalyst bed(s) to meet the treat gas (hydrogen) demand forthat catalyst bed(s) with relatively high kinetic efficiency.

As previously mentioned, countercurrent reaction vessels are typicallysusceptible to upset by flooding. That is, the upflowing treat gas canprevent liquid feedstock and liquid effluent from flowing downwardthrough one or more catalyst beds. FIG. 2 hereof depicts how thereaction vessel of FIG. 1 would operate during a flooding situation toget the reaction vessel back on-stream without substantial downtime. Forexample, during a flooding situation in reaction zone r₂, liquid holdupLF in the bed increases and liquid may begin to accumulate above the topsurface of the catalyst bed. One or more liquid drain means LD areprovided to allow the liquid to bypass one or more catalyst beds. Priorto flooding, the liquid drain means will act as a vapor passageway. Thetop of the liquid drain means can be flush with, or any height above thetop surface of the catalyst bed. It is preferred that the top of theliquid drain means be substantially flush with the top surface of thecatalyst bed. Any liquid that passes through the drain means can bepassed to the next downstream bed or it can preferably be recycled toany one or more of the upstream reaction zones.

The vapor and liquid drain passageways may be any suitable structureconstructed from a material that can withstand the operating conditionsof the reaction vessel. Suitable materials include metals, such asstainless and carbon steels; ceramic materials; as well as highperformance composite materials such as carbon fiber materials.Preferred are tubular passageways. The passageways need not be perfectlyvertical. That is, they can be inclined or curved, or even in the formof a spiral. It is to be understood that the passageways can be of anysuitable size depending on the amount and rate of vapor one wishes tobypass from one nonreaction zone to another. Further, one or more of thepassageways, or drain means, can have a flat substantially horizontalmember, such as a baffle, above it to prevent liquid from an upstreambed from falling into the passageways. Also, more than one passagewaycan be extended through at least a portion of any one or more reactionzones. It is preferred that the vapor passageways be extended entirelythrough the one or more reaction zones. When a plurality is used it ispreferred that they be concentrically located about the vertical axis ofthe reaction vessel. One or more vapor passageways can also be routedexternal to the reaction zone. For example, a tubular arrangement can beused on the outside of the reaction vessel so that one or morenon-reaction zones are in fluid communication with any one or more othernon-reaction zones. The vapor passageways may contain a flow controlmeans to control the portion of vapors which is passed from onenon-reaction zone to another non-reaction zone. If the vapor passagewaysare external to the reaction vessel, then it is preferred that the flowcontrol means be simply a flow control valve.

It is within the scope of the present invention that the vaporpassageways bypass two or more catalyst beds, or reaction zones.Further, the vapor passageways need not be hollow structures, such assolid-walled tubes, but they may contain a packing material, such asinert balls, or catalyst particles, or both. If catalyst particlescompose at least a portion of the packing material in the vaporpassageways, they can be used to further react the vapor phasereactants. The packing material and/or catalyst particles in the vaporpassageways can be of a different size than the catalyst particles inthe catalyst beds of the reaction zones. Such packing may help toimprove the bypassing characteristics of said tubes. The vaporpassageways may also perforated to allow vapor to be distributed alongvarious levels of the catalyst bed. It is preferred that one or moreco-current reaction zones be upstream of one or more countercurrentreaction zones. The zones can be in separate vessels or two or morezones can be in the same vessel. It is preferred that all countercurrentzones be in the same vessel.

The practice of the present invention is applicable to all liquid-vaporcountercurrent refinery and chemical systems. Feedstocks suitable foruse in such systems include those in the naphtha boiling range to heavyfeedstocks, such as gas oils and resids. Typically, the boiling rangewill be from about 40° C. to about 1000° C. Non-limiting examples ofsuch feeds which can be used in the practice of the present inventioninclude vacuum resid, atmospheric resid, vacuum gas oil (VGO),atmospheric gas oil (AGO), heavy atmospheric gas oil (HAGO), steamcracked gas oil (SCGO), deasphalted oil (DAO), and light cat cycle oil(LCCO).

Feedstocks treated by the practice of the present invention will mostlikely contain undesirable high levels of heteroatoms, such as sulfurand nitrogen. In such cases, it will often be preferred that the firstreaction zone be one in which the liquid feedstream flows co-currentwith a stream of hydrogen-containing treat gas through a fixed-bed ofsuitable hydrotreating catalyst. The term "hydrotreating" as used hereinrefers to processes wherein a hydrogen-containing treat gas is used inthe presence of a catalyst which is primarily active for the removal ofheteroatoms, such as sulfur, and nitrogen with some hydrogenation ofaromatics. The term "hydroprocessing" includes hydrotreating, but alsoincludes processes which are primarily active toward the hydrogenation,hydrocracking, and hydroisomerization. Ring-opening, particularly ofnaphthenic rings, for purposes of this invention can also be included inthe term "hydroprocessing". Suitable hydrotreating catalysts for use inthe present invention are any conventional hydrotreating catalyst andincludes those which are comprised of at least one Group VIII metal,preferably Fe, Co and Ni, more preferably Co and/or Ni, and mostpreferably Co; and at least one Group VI metal, preferably Mo and W,more preferably Mo, on a high surface area support material, preferablyalumina. Other suitable hydrotreating catalysts include zeoliticcatalysts, as well as noble metal catalysts where the noble metal isselected from Pd and Pt. It is within the scope of the present inventionthat more than one type of hydrotreating catalyst be used in the samereaction vessel. The Group VIII metal is typically present in an amountranging from about 2 to 20 wt. %, preferably from about 4 to 12%. TheGroup VI metal will typically be present in an amount ranging from about5 to 50 wt. %, preferably from about 10 to 40 wt. %, and more preferablyfrom about 20 to 30 wt. %. All metals weight percents are on support. By"on support" we mean that the percents are based on the weight of thesupport. For example, if the support were to weigh 100 g. then 20 wt. %Group VIII metal would mean that 20 g. of Group VIII metal was on thesupport. Typical hydrotreating temperatures range from about 100° C. toabout 400° C. with pressures from about 50 psig to about 3,000 psig,preferably from about 50 psig to about 2,500 psig. If the feedstockcontains relatively low levels of heteroatoms, then the co-currenthydrotreating step may be eliminated and the feedstock passed directlyto an aromatic saturation, hydrocracking, and/or ring-opening reactionzone.

For purposes of hydroprocessing, the term "hydrogen-containing treatgas" means a treat gas stream containing at least an effective amount ofhydrogen for the intended reaction. The treat gas stream introduced tothe reaction vessel will preferably contain at least about 50 vol. %,more preferably at least about 75 vol. % hydrogen. It is preferred thatthe hydrogen-containing treat gas be make-up hydrogen-rich gas,preferably hydrogen.

In the case where the first reaction zone is a co-current hydrotreatingreaction zone, the liquid effluent from said hydrotreating reaction zonewill be passed to at least one downstream reaction zone where the liquidis passed through a bed of catalyst countercurrent to the flow ofupflowing hydrogen-containing treat-gas. Depending on the nature of thefeedstock and the desired level of upgrading, more than one reactionzone may be needed. The most desirable reaction products resulting fromhydroprocesssing, preferably when gas oils are the feedstocks, are thosecontaining reduced levels of sulfur and nitrogen. Product streamscontaining paraffins, especially linear paraffins, are often preferredover naphthenes, which are often preferred over aromatics. To achievethis, at least one downstream catalyst will be selected from the groupconsisting hydrotreating catalysts, hydrocracking catalysts, aromaticsaturation catalysts, and ring-opening catalysts. If it is economicallyfeasible to produce a product stream with high levels of paraffins, thenthe downstream zones will preferably include an aromatic saturation zoneand a ring-opening zone.

If one of the downstream reaction zones is a hydrocracking zone, thecatalyst can be any suitable conventional hydrocracking catalyst run attypical hydrocracking conditions. Typical hydrocracking catalysts aredescribed in U.S. Pat. No. 4,921,595 to UOP, which is incorporatedherein by reference. Such catalysts are typically comprised of a GroupVIII metal hydrogenating component on a zeolite cracking base. Thezeolite cracking bases are sometimes referred to in the art as molecularsieves, and are generally composed of silica, alumina, and one or moreexchangeable cations such as sodium, magnesium, calcium, rare earthmetals, etc. They are further characterized by crystal pores ofrelatively uniform diameter between about 4 and 12 Angstroms. It ispreferred to use zeolites having a relatively high silica/alumina moleratio greater than about 3, preferably greater than about 6. Suitablezeolites found in nature include mordenite, clinoptiliolite, ferrierite,dachiardite, chabazite, erionite, and faujasite. Suitable syntheticzeolites include the Beta, X, Y, and L crystal types, e.g., syntheticfaujasite, mordenite, ZSM-5, MCM-22 and the larger pore varieties of theZSM and MCM series. A particularly preferred zeolite is any member ofthe faujasite family, see Tracy et al. Proc. of the Royal Soc., 1996,Vol. 452, p813. It is to be understood that these zeolites may includedemetallated zeolites which are understood to include significant porevolume in the mesopore range, i.e., 20 to 500 Angstroms. Non-limitingexamples of Group VIII metals which may be used on the hydrocrackingcatalysts include iron, cobalt, nickel, ruthenium, rhodium, palladium,osmium, iridium, and platinum. Preferred are platinum and palladium,with platinum being more preferred. The amount of Group VIII metal willrange from about 0.05 wt. % to 30 wt. %, based on the total weight ofthe catalyst. If the metal is a Group VIII noble metal, it is preferredto use about 0.05 to about 2 wt. %. Hydrocracking conditions includetemperatures from about 200° to 425° C., preferably from about 220° to330° C., more preferably from about 245° to 315° C.; pressure of about200 psig to about 3,000 psig; and liquid hourly space velocity fromabout 0.5 to 10 V/V/Hr, preferably from about 1 to 5 V/V/Hr.

Non-limiting examples of aromatic hydrogenation catalysts includenickel, cobalt-molybdenum, nickel-molybdenum, and nickel tungsten.Non-limiting examples of noble metal catalysts include those based onplatinum and/or palladium, which is preferably supported on a suitablesupport material, typically a refractory oxide material such as alumina,silica, alumina-silica, kieselguhr, diatomaceous earth, magnesia, andzirconia. Zeolitic supports can also be used. Such catalysts aretypically susceptible to sulfur and nitrogen poisoning. The aromaticsaturation zone is preferably operated at a temperature from about 40°C. to about 400° C., more preferably from about 260° C. to about 350°C., at a pressure from about 100 psig to about 3,000 psig, preferablyfrom about 200 psig to about 1,200 psig, and at a liquid hourly spacevelocity (LHSV) of from about 0.3 V/V/Hr. to about 2.0 V/V/Hr.

The liquid phase in the reaction vessels used in the present inventionwill typically be the higher boiling point components of the feed. Thevapor phase will typically be a mixture of hydrogen-containing treatgas, heteroatom impurities, and vaporized lower-boiling components inthe fresh feed, as well as light products of hydroprocessing reactions.The vapor phase in the catalyst bed of a countercurrent reaction zonewill be swept upward with the upflowing hydrogen-containing treat-gasand collected, fractionated, or passed along for further processing. Ifthe vapor phase effluent still requires further hydroprocessing, it canbe passed to a vapor phase reaction zone containing additionalhydroprocessing catalyst and subjected to suitable hydroprocessingconditions for further reaction. It is to be understood that allreaction zones can either be in the same vessel separated bynon-reaction zones, or any can be in separate vessels. The non-reactionzones in the later case, will typically be the transfer lines leadingfrom one vessel to another. It is also within the scope of the presentinvention that a feedstock which already contains adequately low levelsof heteroatoms be fed directly into a countercurrent hydroprocessingreaction zone for aromatic saturation and/or cracking. If apreprocessing step is performed to reduce the level of heteroatoms, thevapor and liquid can be disengaged and the liquid effluent directed tothe top of a countercurrent reaction vessel. The vapor from thepreprocessing step can be processed separately or combined with thevapor phase product from the reaction vessel of the present invention.The vapor phase product(s) may undergo further vapor phasehydroprocessing if greater reduction in heteroatom and aromatic speciesis desired or sent directly to a recovery system.

In an embodiment of the present invention, the feedstock can beintroduced into a first reaction zone co-current to the flow ofhydrogen-containing treat gas. A vapor phase effluent fraction can thenbe separated from the liquid phase effluent fraction between reactionzones. That is, in a non-reaction zone. The vapor phase effluent can bepassed to additional hydrotreating, or collected, or furtherfractionated. The liquid phase effluent will then be passed to the nextdownstream reaction zone, which will preferably be a countercurrentreaction zone. In other embodiments of the present invention, vaporphase effluent and/or treat gas can be withdrawn or injected between anyreaction zones.

The countercurrent contacting of liquid from an upstream reaction zonewith upflowing treat gas strips dissolved H₂ S and NH₃ impurities fromthe effluent stream, thereby improving both the hydrogen partialpressure and the catalyst performance. The resulting final liquidproduct will contain a substantially lower level of heteroatoms andsubstantially more hydrogen then the original feedstock. This liquidproduct stream may be sent to downstream hydroprocessing or conversionprocesses.

What is claimed is:
 1. A reaction vessel for reacting liquid petroleumand chemical streams with a hydrogen-containing treat gas in thepresence of a catalyst, which reaction vessel comprises:(a) acylindrical outer shell having an enclosed top section and an enclosedbottom section; (b) at least one reaction zone containing a bed ofcatalyst, wherein each reaction zone has a non-reaction zone immediatelyabove and immediately below it; (c) at least one liquid inlet means forfeeding a liquid feedstream selected from petroleum and chemicalfeedstreams and at least one vapor outlet means at a location upstreamfrom the uppermost reaction zone in relation to the flow of said liquidfeed stream; (d) at least one liquid outlet means and at least onehydrogen-containing treat gas inlet means at a location downstream ofthe lowermost reaction zone in relation to the flow of said liquid feedstream wherein each of said at least one hydrogen-containing treat gasinlet means is in fluid communication with a source ofhydrogen-containing treat gas; and (e) at least one vapor passagewaymeans which allows a portion of the gas to bypass at least a portion ofat least one reaction zone so that said portion of the gas can flowupward from one non-reaction zone below said reaction zone to anon-reaction zone above said reaction zone without coming into contactwith all of the catalyst of the catalyst bed of said reaction zone it atleast partially bypasses; and (f) at least one liquid drain means whichbypasses at least one reaction zone, thereby allowing liquid to passthrough said reaction zone without contacting the catalyst of saidreaction zone.
 2. The reaction vessel of claim 1 wherein said at leastone reaction zone comprises at least two reaction zones.
 3. The reactionvessel of claim 2 wherein each reaction zone contains at least one vaporpassageway means.
 4. The reaction vessel of claim 3 wherein at least oneof said at least one vapor passageway means extends entirely through atleast one reaction zone.
 5. The reaction vessel of claim 4 wherein allof the vapor passageway means extend entirely through the reaction zonesin which they are located.
 6. The reaction vessel of claim 3 wherein atleast one of said at least one vapor passageway means is locatedexternal to at least one reaction zone.
 7. The reaction vessel of claim6 wherein said at least one vapor passageway means which is locatedexternal to at least one reaction zone contains a means for adjustingthe quantity of gas flow through said at least one vapor passagewaymeans.
 8. The reaction vessel of claim 1 wherein said at least one vaporpassageway means is tubular.
 9. The reaction vessel of claim 2 whereinsaid at least one vapor passageway means bypasses two or more reactionzones.